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Mode of action:


Inhibition of protein synthesis.  Macrolides reversibly bind to 50S subunit of the ribosomes and inhibit transpeptidation and translocation processes, resulting in premature detachment of incomplete polypeptide chains. 



Macrolides approved for veterinary use: Erythromycin, Tylosin, Spiramycin, Tilmicosin, Tulathromycin



Saccharopolyspora erythaea (Erythromycin)

Streptomyces fradiae (Tylosin)

Some are semisynthetic (Tilmicosin, Tulathromycin)


Spectrum of activity:

Narrow spectrum


Effect on bacteria:

Generally bacteriostatic, but may be bactericidal at high concentrations or if there are a low number of a highly susceptible bacterial organism.


Examples of applications in Veterinary Medicine:

Erythromycin – drug of choice against Campylobacter jejuni. Can be an alternative to penicillin in penicillin-allergic animals and second choice for anaerobic infections.


Tylosin and spiramycin – used against Mycoplasma infections; used as growth promotants.


Tilmicosin – against Mannheimia, Actinobaciullus, Pasteurella, Mycoplasma;




Parenteral use of tylosin in horses has been fatal, while oral administration has no indication for use and might result in enterocolitis.


Tilmicosin can be fatal to pigs if given parenterally, and is not recommended for use in goats due to toxicity.





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